Fibromyalgis = Pain in all 4 quadrants of the body, as well as in the axial skeleton continuously for at least 3 months and the presence of at least 11 of 18 anatomically specific tender points. Tender points are painful areas when pressure (4 kg) is applied, without referred pain.

Disturbances within the central nervous system (CNS) known as central sensitization represent the most likely etiology.